The Wall Street Journal vs. The Scientific Consensus

June 22nd, 2005 by group

This is incorrect. The natural causes of past climate variations are increasingly well-understood, and they cannot explain the recent global warming. As discussed elsewhere on this site, modeling studies indicate that the modest cooling of hemispheric or global mean temperatures during the 15th-19th centuries (relative to the warmer temperatures of the 11th-14th centuries) appears to have been associated with a combination of lowered solar irradiance and a particularly intense period of explosive volcanic activity. When these same models are forced with only natural radiative forcing during the 20th century [see e.g. Crowley (2000)] they actually exhibit a modest cooling trend. In other words, the same natural forcings that appear responsible for the modest large-scale cooling of the “Little Ice Age” should have lead to a cooling trend during the 20th century (some warming during the early 20th century arises from a modest apparent increase in solar irradiance at that time, but the increase in volcanism during the late 20th century leads to a net negative 20th century trend in natural radiative forcing). In short, given natural forcing factors alone, we should have basically remained in the “Little Ice Age”. The only way to explain the upturn in temperatures during the 20th century, as shown by Crowley (2000) and many others, is indeed through the additional impact of anthropogenic (i.e., human) factors, on top of the natural factors.

Most global warming alarms are based on computer simulations that are largely speculative and depend on a multitude of debatable assumptions.

This is not correct. Concern about global warming is not based primarily on models, but rather on an understanding of the basic physics of the greenhouse effect and on observed data. We know from data that we have caused the CO2 concentration in the atmosphere to rise sharply during the past century: it is now much higher than any time during the past 650,000 years (which is as far back as reliable ice core data exist). And we know that this rise in CO2-concentration changes the radiation balance of the planet and leads to a warming of global surface temperature. This is scientifically undisputed and well-established physics, which has been known since in the year 1896 the Swedish Nobel prize winner Svante Arrhenius calculated the climatic effect of a rise in CO2.

Since there is a continued increase in emissions of (in particular) CO2, continued greenhouse warming is highly likely to continue. The models serve merely to quantify these basic facts more accurately, calculate the regional climate response, and compute effects (such as the expected increase in ocean heat content or sea level) which can be tested against observed data from the real world.

The editorial then returns to the issue of paleoclimate reconstructions and the so-called “Hockey Stick”, repeating literally each of RealClimate’s documented “Hockey Stick” myths:

Then there’s the famous “hockey stick” data from American geoscientist Michael Mann. Prior to publication of Mr. Mann’s data in 1998, all climate scientists accepted that the Earth had undergone large temperature variations within recorded human history.